"My preference is to have an SSD as my system drive as it will boot almost immediately in the case of crisis or quick changeovers at festivals etc"
Another reason for SSD is that in environments where there can be thunderous bass, in many modern laptop drives, there’s an auto G sensor, which tells the drive to park it's heads, when there’s any sudden movement - protectiing it from damaging the drive should it be dropped. The vigorous vibration can trigger this and cause the reading of audio files to be seriously hampered. With an SSD, there’s no drive heads, so they dont suffer from the same problem. Of course SSD drives are still pretty costly but if you are working on a production of any scale, it's a must-have upgrade.
5) Go With What You Know
"Go for a tried a tested audio interface with good driver history. I have personally used MOTU ultralites live for the last 6 years with not one problem even using them bus powered."
There are of course other interfaces, many are perfrectly capable of being used in a live environment, but you will probably start to notice that MOTU do have quite a strong presence in live setups.